Some of his troops were marching until midnight to get there.

Receiving here early on the 16th a repetition of his order to join Johnston at Clinton, he concluded to obey, and sent a dispatch to his chief, informing him of the route by which he might be expected.
About five o'clock in the morning (16th) two men, who had been employed on the Jackson and Vicksburg railroad, were brought to me.

They reported that they had passed through Pemberton's army in the night, and that it was still marching east.

They reported him to have eighty regiments of infantry and ten batteries; in all, about twenty-five thousand men.
I had expected to leave Sherman at Jackson another day in order to complete his work; but getting the above information I sent him orders to move with all dispatch to Bolton, and to put one division with an ammunition train on the road at once, with directions to its commander to march with all possible speed until he came up to our rear.

Within an hour after receiving this order Steele's division was on the road.
At the same time I dispatched to Blair, who was near Auburn, to move with all speed to Edward's station.